LightBringer is right about the rules on reducing level adjustment. A pixie with a LA of +4 can buy off its first level at 12th, its second at 21st, its third at 27th and its fourth at 30th. This means that only a +3 LA can be bought off entirely until level 25 according to the RAW. Unless I'm making a mistake myself.

“

If something has 4 hit dice and a LA of +2, why didn't they just say the LA was +6 to begin with?

”

That's a very PC-ey way of thinking. Think of a creature with a level adjustment of +6 and... uh... two HD or class levels? It's way too dead way too quickly. Therefore they decided to make up for the benefits of a race by giving it LA on the one hand and the weaker HD on the other.

This whole campaign sounds like an adventure in its entirety. I'll be watching with interest.